Why doesn't avast ignore the file/folder I excluded? Is there another way to exclude files?
Sure, there are actually two exclusion lists: one in program settings, affecting the on-demand scanners, and another one in Standard Shield settings, affecting Standard Shield (i.e. on-access protection) only.
Second, it's necessary to put the complete mask to the exlucions, i.e. something like
C:\Programs\GT2\*
or
*\gtdata.dll
I'd rather suggest the later, because of potential problems with long file names in the first case.
Oh, there is the WebShield exclusion list for websites too